Continuous process for separation of waxlike constituents from oil



July 22, 1952 w. E. sKELToN ET AL 2,604,430

CONTINUOUS PROCESS FOR SEPARATION OF wAxLIKE cONsTITuENTs FROM OIL Filed Feb. 24, 1949 VCl/l/M JET Fez-:n ou,

j AzlTaNExg Patented July 22, i952 William E. Skelton, Beacon, AIrvine German, J r., Y New York, Howard A. Kirsch, Beacon, andl Walter V..0verbaugh, Fishkill, N. Y., assignors to The Texas Compan j Y poration of Delaware y, New Xorlr, N.- Y., a. cornppiiation February 24, 1949, serial-Ne. 78,022.

1 .Thisfinvention relates to a continuous process for'vsep'aration ofwax-like consttuents'from oil such as'contained in hydrocarbon mixtures by treatmentwith anr organic agent such as urea.v

. The invention concerns a continuous process for separation of Wax vandvvax-like constituents from 'oil by treatmentwith an organic vcomplexing.' agent having the structure:

\N'Hz l K where X may be either oxygen or sulfur.- Examples of eifective compounds or agents arev urea and thiourea, which are capable of forming with waxy-constituents of lmineral oil solid crystalline complex compounds readily separable fromA the oilz'-v f z The invention involves effecting contact; be'- tween feed oil and complexing agent in thel presenceof a polar solvent liquid containing-an hydroxyl group under conditionsy such that formationfof theY foregoing crystalline 'complex occurs. Polar solventf liquids such as aliphatic alcohols which exert appreciable solvent f action `on the complexing agent at temperatures in the range of 125 F. and lower, and substantially increased solvent action at higher temperatures, are efec-, tive solvents for the process of this invention.- Advantageously the solventis at least partially miscible withthe oil. In addition the solvent liquid is one which is capable of forming azeotropes withfwater. l I As a result of contact between the feed oilfami thecomplexing agent in the presence of the polar solvent there is obtained a slurry or mixture contaming solid crystalline complex, oil, excess complexing agentfancl solvent. Depending upon the temperature used and the relative amounts of the various componentswhich are present in the foregoing mixture, there may be either one or two distinct liquid phases or layers present, i. e., an oil rich phase yandy a solvent rich phase. Also; in

addition to the crystalline-complex, the solid material'may include excess solid 'complexing'agent over 1and above'the amount which enters directly into `complex formation. AThissaid solid material `is separated. by suitable 'means from the liquid layer or layers 'The solid material is treated to break the complex and separately 'recover its components, the recovered complexing agent and solvent being returned for reuse'inthe process. The liquid layer, or layers are treated to recover components thereof.

2 claims. (ci. 1%;1'7)

The present invention is particularly concerned with the recovery of solvent liquid and complexing agent. Y, Thus in accordance with this invention-the crystalline complex-material after separation from ,the-, liquidgmediu'm is treated with an azeotropic mixture of solvent and water under conditions eiective to decompose the complex with liberation of oily constituents therefrom and forming asolution ofcomplexing agent vin solvent liquid.A The azeotropic mixture used inY this treatment is obtained by azeotropic distillation of solvent-rich liquid or liquids subsequently recovered from the complex and alsorecovered from complex-free or relatively complex-free oil.

The complex-free.'or relatively complex-free,- oilretains some .residual -complexing agent and in accordance withthe process of this invention it is also treated withga portion of the afore-y mentioned azeotropic mixture under conditions eifective to extract theresidual agent therefrom.

. The resulting extract solution fromthis latter operation as well as that obtained inthe decomposition of the complex provide kthe-feed tothe azeotropic distillation. From =this distillation there is obtained a Vresidual liquid consisting essentially of solvent and dissolved complexing agent which is recycled kfor use yin treating fresh As Will'r be seen from the subsequent detailed description of the invention, it provides a continuous new operation. A rcomplexing agent is recovered and handled'in theform of asolution so'that it is easily transferred Within the system byxconventonal pumps. This avoidsresort to crystallization or evaporation in therecovery of the complexing agent for return to the initial contact With feed oil. Moreover it ap-` pears that the azeotropic mixture of solvent and' Water provides anexcellent medium'for recov-I ering theused .complexing agent from both the solid complex and the complex-free or relativelycomplex-free oil.

In order to describe the invention in more detail reference 'will' now be made to *th-eV accompanying drawing in which Fig. 1 comprises a eating oil'stock such as used in the manufacture of refrigerator lubricating oils.

and having apour test of minus 25 F;

Such stockmay have afSayboltUniversal viscosity of 300 seconds' at .F., containing about 1.0% Wax byvolumeV exchanger 2 to a mixer y3. Prior to passage through the exchanger 2 the -oil is commingled with a stream of normal propyl alcohol saturated or substantially saturated with ureaat a temperature. of" 1205?"Fgjto 200 'Ibis'.jsolutionzvs conductedv `through a pipe from afsubse'q'uent point in the system and torWhich reference will be made later.

Since the alcohol-urea mixture. is atlelevate temperature it is advantageoustopassi-thev re..

sulting mixture through the exchanger 2 wherein iswithdrawn through pipe 22 and comprises api-t is cooled to a temperature in theirange-ofjabout' 70 to 125 F. and such that' solidiurea,s-presenti* in the mixture.

If desired, a mixing vesselprovide'd with accol-r` ing coil may be used in which case the feed oil and the hot urea solution may'be,separately:'in-

troduced into the vessel and subsequently .re-V

duced to the aforesaid temperature at which urea crystallizes from the alcohol. Cooling maybe eiecteciA by evaporative means as -Willfbedescifibed withreferencetoFigure'HSL- l The amount of"ure`a added-` to-` lie-feed'- oilf may amount Vtoy about 3 toipar'tsby-Weightfof th'eWaX constituents of the oil; While alcoholgm'ayf amount tof-rom aboutl to 3 volumes pervolumeoffed oil' Wa-xconstituents quickly -e-nter' into complex formation'with- "theA ureaV` forming'acrystalline complex consistingfxof aldoi'i'tv 25% Wax-andA A753%! ureafby Weight. Xlray' analysis of" thehcomplex indicates that the urea crystal which isnofrmally tetra-gonal'in form tr'a-rlsiorms-itself intola hex.- agonall systemv in the resultingcrystalline com'- plex; K The resulting mixture porl slurry/- of crystalline* complexgoil and solvent liquid is passedinto-asettle'r maintainedat sfubstar'itia-llfy the1 contact'-m ing' temperature to` permiti-stratiicatiorr into- 'The upper'la-yer cemprisesi'a solventi-rich phase containing crystalline complex and it is drawniiftlflrou'gl'i` pipe Sftola filter 9`. f Y' f Theif'lt'er may bergaf conventional continuous rotaryv drum lter. .Asfaresultioiltration. there iS-f'ormeda lter-cake of crystalline complex and. comprising for example about 427% urea, 33.3%- vvax and oil, 24.0% alcohol. This filter-'cake isy discharged through: pipe I.I. "Filtrato obtained is Vdischarged through pipe I2 vand willi. comprise. approximately 6`1.'.3%..oil, 1.7%'.'urea'and 3.7%: alcohol. This-filtrate is passedto'. an azeotropicndisti-l#4 lation column I 3 whereirr it: isv used:A to. carry'A inv solution frorrllsaiel` column .f3.ur`ea. which:is introduced.. to. 'said' columnidli' the streams in; pipesidand Z2... .From the column is taken Yoverhead :a' distillate: azeotro'pe;`- consisting of about 28.3%Waterand= 71.7%."azl'cohol'. lThe distille.r tion carried out at-aboutatmospheric presisuremaintaininga .temperature of4 about 225" F. at the bottom of the column and'. a: tempera@ ture of about. 1905" Rat the topl thereof'.

The.l distillate is: remo-ved through. pipe i5 and'. condenser I5. A Y f A portion thereof', for example abouti/3h51 vol-Li ume "isfdiverted through pipe I1 .tovl pipe I I throughfwhich the lterlc'ake is. conducted. The

. cakefand; azeotrope'aresubjected to mixi-ngxin` a mixer `I3:at1"a.temperature oizabouti- 1'6.31E?`.V andk then. passed into 'a settlerl'; m'aintainedat substantially thef'same. temperature'and. approxi-4 mately atmospheric: pressure. At'fthi-s elevated temperature the complex'breaks down Withliberation of Wax constituents therefrom'.` In the proximately 242% urea, 58.2% alcohol and 17.6% water.r Thisliquid mixture is passed into the .previously'mentionedcolumn I3 wherein it is subected Ito Yazeotropic" distillation.

*Thefoi-l--riclr phase accumulating in the lower 'port'ion'j ofthe; settler 'l is drawn off through pipe "andrwi`ll comprise approximately 21% alcohol, 'Z8A.%-joil' andf 9.66% urea. This stream is passed to a mixer 3l wherein it is commingled With the i remaining portion `of the azeotrope stream flowing through pipe I5 and being diverted through pipe.- Iz; mixing; is. effected'.` ait.- a tempera tureof. about `1;(10. .F.. ther-esulti'ng mixtureV ing through. themixerf'I': comprises; aboutZBn/z Water',.25 .l alcohol; 7.1.13 oilzanc. 0.645975-` urea. This. mixture: flows into a. settler-,32: .maintained atabout: 100f'Fg. Whereirrrstraticatiori.intoilayers occurs.. The; upper;Y layer: comprising' mainlygal cohol and containing,"snrallfamounts ofoilis drawn oil through pipe. 33 and returned by pipe 34 to the column I3.

The bottom layer is drawn off from settler 32 through pipe 36 and. comprises about 93.65% oil, 6.30% Water-alcohol, 0.65% Vurea. This stream isv con-ducted throughA pipe :to a stripper 3'1" wherein. it is; subjectedtio` distillation advanta geously' at'. atmospheric` pressure and: ata tem-- peratureL-in therangeiofil95i to'BOOE'F; such that alcohol 'andwater are. ydistilled from the de@ Waxed oil. The resulting distillate is remove-dv5 throughpipe 38land-passed into. pipe.- 3'41 for charging'toithewcolumn. 'f r Solventf-freerdewaxed oilis .removed fromithe bottom ofstripper: 31a .temine-39u; .Thus Withedrawn: oit may .beisubjected'td washing:v or such other"trea-tn'ient.v as: mayfbe necessary :toremove. the small lamounts of residuallfcomplexing' agent retained.' therein.. l 1 Y l IFrom.l theA bottomfof the distillate co'liirnnf [3i there. is drawnoff through.; pipe. MT a.. residuali l-iqf-1 ui'd'zfraction consisting essentiallyof alcohol andi dissolved urea with. some. oil,. the`r urea. amounting'to'about 5l to. l10% by' Weight off-thel solvent'. This lsolution is. conducted to previously` men#V tioned pipe 5 by which it is recycled for.- treating fresh: feed oil.

VThe:vatorernentioned: dewaxed'. oil removed from pipe 35i-Will havev a pour testof about minus 252: Fi. However itiwill have a.l'reon` Haze 'test'fof about .minus to minus 75 F. as compared with about'minus 22F'. for'thefeed oil.

#The aforesaid' Freonf'Haze is determined by' mixing the oilWith-Freon- 12?? (-dichloro d-ifl-uforo methane) inthaproportio'n'of about 90% Freon 12. to 10% oil'eand chilling the mixture totheA point. zit-Which Wax haze appears.

1 As .previously indicated.- 'evaporative-1 cooling may'xibe. use/df in place of vthe exchanger 2. 'Thus referring to Figure/.IL the. hot" alcohol-urea stream frompipe 5 iszczommingle'd with the feed' oil streamV in. pipe., I; and the resultingmixture. passed'into a vessel :2u provicledfzwith stirring mechanism' as' indicated". Affreducec pressure is maintained thereinjsuch :that evaporation "ot"'alcol'l'ol from the mixture occurs withy refrigerativ-e.effect.v` The alcohol vapors are removed through pipe- A and condenser 50 which discharges into a receiver 5I which communicates through pipe 52 with a vacuum jet or other means for reducing the pressure. Condensate is discharged through pipe 53. Alcohol removed as condensate can be reused in the system. Provision may be made for adding additional alcohol to the oil mixture entering cooler 2a in order to supply the necessary evaporation for cooling.

The slurry accumulating in the bottom of cooler 2a is drawn off through pipe 6 to the settler 7 of Figure I.

While mention has been made of employing a lter 9 it is contemplated that other means may be employed such as centrifuging, settling or thickening to effect separation of the crystalline complex from the solvent-rich phase.

, While normal propyl alcohol is a preferred polar solvent for carrying out the process, nevertheless it is contemplated that other materials may be employed or other polar solvents having the requisite solvent characteristics as previously defined.

Although the specific example refers to the treatment of a low wax content feed oil, nevertheless itis contemplated that the process may have application to the treatment of other wax-bearing mineral oils and also to the treatment of wax concentrates etc. In the case of the more viscous or higher molecular weight feeds, it may be advantageous to employ a non-polar solvent liquid as a diluent, examples of which are the conventional hydrocarbon solvents such as petroleum naphtha or naphtha hydrocarbons. Oil derived from other sources such as animal. vegetable and marine sources may be treated in accordance with this invention.

Urea enters into complex formation with certain naphthenic and aromatic compounds having long aliphatic side-chains and also enters into complex formation with oxygenated compounds. Accordingly, the process may be used in the separation of constituents other than wax from oil or oily substances containing them.

While urea has been specifically mentioned, it is contemplated that substituted derivatives, such as ethanol urea, diethyl urea and butyl urea may be used as well as other derivatives containing various di-, triand/or tetravalent inorganic and/or organic compounds.

Obviously many modifications and variations of the invention, as hereinbefore set forth, may be made without departing from the spirit and scope thereof, and therefore only such limitations should be imposed as are indicated in the appended claims.

We claim:

1. In a continuous process of separating wax from a feed mixture of wax and oil by contact with a complexing agent having the structure:

where X isA selected from the group consisting of Oxygen and Sulfur, the method comprising contacting the feed oil in a contacting zone with said agent in the presence of a low molecular weight aliphatic alcohol, forming in said zone a mixture of solvent, oil and crystalline complex of wax and said agent, stratifying said mixture at a temperature of about '70 to 125 F. into a primary oilrich layer and a primary solvent-rich layer containing crystalline complex, separately withdrawing said primary layers, commingling withdrawn oil-rich layer with a portion of an azeotropic mixture of alcohol and water obtained from a source referred to later to form a first commingled mixture, subjecting said first commingled mixture to settling at a temperature of about F. to form a secondary alcohol-rich layer and a secondary oil-rich layer, separately withdrawing said secondary layers, distilling alcohol from withdrawn secondary oil-rich layer to leave a substantially Wax-free oil, discharging said Wax-free oil, mixing said distillate with said secondary alcohol-rich layer, passing the last mentioned mixture into the intermediate portion of a steam distillation tower, filtering from said primary solvent-rich layer a filter cake of crystalline complex and forming a filtrate comprising mainly alcohol, passing said filtrate to the intermediate portion of said steam distillation tower, mixing said lter cake with another portion of said azeotropic mixture of alcohol and water obtained from the aforesaid source referred to later, subjecting this last mentioned mixture to heating at elevated temperature suicient to decompose the complex and liberate wax, discharging liberated wax from the hot solution of complexing agent in solvent, passing discharged hot solution into the upper portion of said steam distillation tower, injecting steam into the lower portion of said steam distillation tower, effecting steam distillation therein to form an azeotropic distillate of alcohol and water, and using said distillate as the source of the aforesaid azeotropic mixture of alcohol and water.

2. The method according to claim 1 in which the complexing agent is urea.

WILLIAM E. SKELTON. IRVINE F. GERMAN, JR. HOWARD A. KIRSCH. WALTER YV. OVERBAUGH.

REFERENCES CITED The following references are of record in the tile of this patent:

UNITED STATES PATENTS Shell Development Co. of German application B. 190,197 (Bengen) deposited in Library of Congress May 22, 1946 (included in Index released May 31, 1946) 5 pages, pages 2-6, inclusive, only. 

1. IN A CONTINUOUS PROCESS OF SEPARATING WAX FROM A FEED MIXTURE OF WAX AND OIL BY CONTACT WITH A COMPLEXING AGENT HAVING THE STRUCTURE: 